Process of forming alloys



J. O. BETTERTQN PROCESS OF FORMING ALLOYS Filed April 13, 1933 Jan. 2, 1934.

INVENTOR ATTORNEYS Patented Jan. 2, 1934 PATENT OFFICE PROCESS OF FORMING ALLOYS Jesse Oatman Betterton, Metuclien, N. 1., as-

signor to American smelting and Refining Company, New York, N. Y.,

New Jersey a corporation of Application April 13, 1933, Serial No. 666,040,

and in Canada December 23, 1932 9 Claims.

The present invention relates to the formation of metal alloys by reacting an alkaline earth metal carbide with molten metal to decompose the carbide into its elemental constituents thereby liberating the alkaline earth metal which enters the molten metal to form the desired alloy and is an improvement of the process described and claimed. in my co-pending application Serial No. 437,603, filed March 20, 1930.

More specifically, the present invention relates to an improved process for effecting the above alloying reaction by which metal alloys, for example, lead and/or zinc, may be formed possessing an alkaline earth metal content approxi- 15 mately 50% in excess of the alkaline earth metal content of similar alloys produced in accordance with the generally accepted standard methods of forming such alloys when carbides are used as the source of alkaline earth metal. In addi- 29 tion, the improved process gives increased overall yields, often as large as 10% to over those heretofore obtained.

An important feature of the present improved process is the continuous cycle of circulation employed by which the alkaline earth carbide particles are caused to alternately and repeatedly react with the molten metal forming the base of the desired alloy and a suitable cleansing and dissolving flux or slag which results in the progressive enrichment of the alloy base metal with the alkaline earth constituents while the carbide particles are correspondingly depleted of their alkaline earth metal content. Another feature of the new process is the use of carbide particles of a special size which are generally known to the trade as pea size and which possess ageneral average diameter of from .25 to .75 inches. The invention also provides special mixing features which assist in securing the markedly superior results obtained by practising the present improved process.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, and the manner in whichit may be carried out, may be better understood by referring to the following description taken in connection with the accompanying drawing forming 50 a part thereof, in which is shown one type of apparatus for practising the invention. 6

In the drawing, '10 represents a kettle for containing the molten metal. The kettle may be heated from any convenient source not shown 55 and is supported by suitable beams 11. A suitable stirring assembly is mounted on transverse beams 12 which extend across and are supported by the rim of the kettle 13. A rotatable paddle 14 is associated with gears 15 and is driven by a source of power not shown connected with drive shaft 16. A suitable adjusting means 1'7 is provided to regulate the position of the paddle 14 in the molten bath. Paddle 14 is suitably inclined to impart a downward and outward motion to the metal being treated which causes a well-defined e5 vortex 18 to form in the central portion of the bath and produces a circulation as indicated in the drawing.

In accordance with the present invention, a molten bath of a desired metal, for example, lead or zinc, may be established in a kettle or other suitable container and covered with a suitable slag. The cover slag may comprise practically any of the higher halogen salts of the alkali or alkaline earth metals including magnesium or suitable mixtures thereof, although salts or mixtures possessing relatively high melting points should be avoided. In manufacturing calciumlead alloys, eflicient results have been secured using slags comprising calcium chloride alone, a so mixture of calcium chloride and sodium chloride or a mixture of calcium chloride and calcium fluoride.

Appropriate quantities of pea size carbide of the desired alkaline earth metal may then be 35 added to the kettle containing the molten metal and salt cover and the contents agitated in such manner that the carbide particles are alternately and repeatedly exposed to the action of the slag and the metal of the bath.

This continuous alternating reaction and contact of the carbide particles with the slag and bath may be effectively carried on by inserting in the bath a suitable mixer having an impeller adapted to create a vortex in the bath through which the carbide particles are drawn from the slag down into the molten metal where they surrender part of their alkaline earth metal content and are returned to the slag by the action of the impeller which throws them outwardly and up- 106 wardly along the bottom and sides of the kettle.

It has been found that by operating the mixer at a speed of approximately to 300 revolutions per minute for a period of from six to ten hours that proper circulation is maintained to effect the formation of alloys having an alkaline earth metal content at 3% to 3.5%.

v The process may be satisfactorily practiced within a temperature range of approximately 1300-1400 F., and these temperatures have ordinarily been used, but equally satisfactory results have also been obtained within a temperature range of 1250-1300 F. To insure a constant and uniform temperature and to avoid heat losses, the kettle is preferably covered during the operation.

The following specific example of the invention as applied to the manufacture of calcium-lead alloys is given to more fully illustrate the manner in which the invention may be practiced:

Approximately 1000 pounds of a calcium chloride-sodium chloride mixture were placed in an ordinary refining kettle, as illustrated in the drawing, and heated to a temperature of approximately 1300 F. to properly fuse and dehydrate the salt mixture. To the fused slag, eight tons of lead were added and, thereafter, the impeller, capable of adjustment from approximately 9 inches from the bottom of the kettle when in its lowest position to a position approximately 21 inches from the bottom of the kettle when in its highest position, was installed in the molten bath for the purpose of agitating same to effect circulation of the carbide particles alternately between the slag and the bath. The impeller was then caused to rotate in the bath thus forming a vortex to which approximately 1200 pounds of pea size carbide were added gradually and uniformly.

The mixer was operated at an approximate speed of 125 revolutions per minute for the first two hours, after which the speed was gradually increased during a period of four hours to 250 revolutions per minute. This speed was maintained for an additional two hours when the operation was complete. During the entire mixing period the kettle was kept covered to insure a constant temperature of approximately 1300- 1400 F. within the bath. The calcium-lead alloy was then removed from the kettle and found to analyze approximately 3.5% calcium.

The following hypothesis is offered as an explanation, in part at least, of the improved results and technical advance in the art accomplished by practising the present invention:

In addition to small quantities of various impurities, commercial carbide, for example, calcium carbide, contains considerable quantities of oxide, for example, calcium oxide. It is generally believed that this oxide exists as a eutectic with the carbide and is diffused and distributed throughout the carbide particles. Thus a typical sample of commercial calcium carbide will contain, say, 20% CaO and the carbide particle, instead of consisting of pure CaC2, really comprises CaCz permeated with a relatively large quantity of the CaC2CaO eutectic which holds the CaCz in a sort of net. As the CaO is inert toward the lead or other metal forming the base of the alloy to be formed, the alloying action, whereby the molten metal reacts with the carbide to form the desired alloy and release free carbon, is retarded and limited to the amount of carbide directly exposed to the molten metal.

Hence, by alternately exposing the carbide particle to the cleansing and dissolving action of the slag and then to the action of the molten metal 0 f the bath, the oxide, which normally prevents sufiicient exposure of the carbide to the molten metal, is repeatedly removed, additional and increased quantities of carbide enter into contact with the molten metal and the bath is progressively enriched in its alkaline earth metal content. In other words, the present invention, by providing continuous circulation of claim 1 characterized in the carbide particles whereby they alternately and repeatedly react with the slag and molten metal, insures a continued and constant exposure of carbide, free from interfering oxide, to the molten metal. As has already been pointed out, this effect may be secured by em ploying a suitable mixer operated at proper speeds.

In addition, the use of carbide particles of a special size, namely, pea size, is an important factor in securing the beneficial results already mentioned. The pea size particles are advantageous in many respects. In the first place, oxidation losses are materially reduced. When fine carbide particles, for example, flour size, are employed the particles diffuse more or less throughout the slag and tend to rise to the surface thereof. On the other hand, the pea sizc particles, as they return to the slag from the bath, do not exhibit this same tendency to rise to the surface of the slag but are mostly confined to the lower regions thereof. Hence, oxidation losses and the corresponding decreases in efiiciency attending same are greatly reduced by employing pea size carbide particles and no need exists for employing neutral or reducing atmospheres over the kettle.

Again, circulation of the carbide between the slag and molten metal is readily effected when pea size particles are used, while with finer sizes it is exceedingly diflicult to pull the fine particles through the slag and into contact with the molten metal of the bath.

While the foregoing explanation is not to be considered as binding upon the applicant, it is believed, in view of what facts are known, to reasonably explain why lead-calcium alloys, for example, may be produced by the improved process of the invention having a calcium content of from 3% to 3.5% as contrasted with calciumlead alloys having a calcium content of only 1.5% to 2.5% when formed by methods hitherto considered standard.

While the term alkaline earth metals has been used throughout the present specification and claims, it is understood to include magnesium. Also, while the manufacture of lead and/or zinc alloys has been specifically mentioned, other metals, such as cadmium, aluminum, tin and the like may be used.

While certain novel features of the invention have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. Process of forming metal alloys which comprises adding an alkaline earth metal in carbide form to a molten metal bath sealed with a suitable cover slag and vigorously agitating said bath in a manner adapted to alternately and repeatedly expose the carbide particles to the cleansing and dissolving action of the slag and to the alloying action of the molten metal.

,2. Process for forming alloys according to that carbide particles of pea size are employed. 1

3. Process of forming alloys of lead and/or zinc with alkaline earth metals which comprises adapted to alternately and repeatedly expose the carbide particles to the cleansing and dissolving action of the slag and to the alloying action of the molten metal.

4. Process according to claim 3 in which the operation is conducted within a temperature range of approximately l250 F. to 1400 F.

5. Process of forming calcium-lead alloys which comprises establishing a molten bath of lead covered with a slag containing a halogen salt of an alkali or alkaline earth metal, adding predetermined quantities of pea size calcium carbide to said bath and agitating said bath in such manner that the carbide particles are alternately and repeatedly brought in contact with the molten lead and slag thereby progressively depleting the carbide oi its calcium content and progressively increasing the calcium content of the lead.

6. The method of freeing an alkaline earth element from its carbide and utilizing the released alkaline earth element as a constituent oi a metal alloy which comprises alternately and repeatedly reacting the carbide with a suitable cleansing and dissolving slag and molten metal iorming the base of the desired alloy.

7. Process according to claim 8 characterized in that the alternate and repeatedreaction between the carbide and the slag and bath is accomplished by a mixing-machine operated at a speed of from 100 to 300 revolutions per minute.

8. In the formation of alloys of calcium and lead, the improvement which comprises establishing a molten bath 01' lead, covering same with a chloride slag in which are incorporated pea size particles of calcium carbide and agitating the bath in such manner as to alternately and repeatedly eflect intimate contact of the carbide particles with the slag and the molten lead.

9. In compounding a lead-calcium alloy, the method that comprises establishing a bath oi! molten lead covered with a calcium chloridesodium chloride slag and causing particles or calcium carbide to continuously circulate in intimate contact between said slag and said molten lead whereby the particles are alternately cleansed of oxide coatings and reacted with the lead with the production of carbon. and the desired calcium-lead alloy.

JESSE OATMAN BETTERTON. 

